In an interview with the New York Times on Tuesday, Hawass said that the thieves took two skulls from a research lab before being stopped as they tried to leave the museum.
Wafaa El Saddik, former director of the Egyptian Museum, confirmed to Discovery News that the mummies had been in a research lab.
"These mummies were kept in a special room at the west side of the museum and they were in the university clinic for some research. They are unknown persons," El Saddik, who led the museum until a month ago, told Discovery News.
The new information makes it even harder to guess who the mummies might be.
"They might never have been in display," Phizackerley said.
Researchers were particularly intrigued by one mummy, whose ripped-off head was photographed amid bones scattered across the floor.
Egyptologist and anthropologist Jasmine Day from Perth, Australia, agrees: "Many of the royal mummies have distinct facial features and even intact hair. The damaged mummies and bones appear to have been knocked accidentally -- or tossed vindictively -- off a table or shelf in the darkened storeroom."